Optical subassembly for in-and/or out-coupling of electromagnetic radiation into, and/or out of, a pressure-tight housing

Abstract

An optical subassembly for in- and / or out-coupling of electromagnetic radiation of a predetermined wavelength, especially IR-radiation, into, and / or out of, a pressure-tight housing. The subassembly includes at least one housing wall section of the pressure-tight housing having at least one opening, wherein, in the opening, mechanical setting means are provided, with which a plug transparent for the electromagnetic radiation is set, wherein the transparent plug has two mutually oppositely lying, base surfaces and a cylindrical lateral surface, and wherein the setting means include as least one setting ring, characterized in the a volume region between at least a first section of the setting ring and at least a section of the cylindrical lateral surface is filled with a pressure-tight, potting compound.

Description

TECHNICAL FIELD[0001]The invention relates to an optical subassembly for in- and / or out-coupling of electromagnetic radiation of a predetermined wavelength range, especially IR-radiation, especially in the wavelength range of 4 to 15 μm, into, and / or out of, a pressure-tight housing.BACKGROUND DISCUSSION[0002]Such an optical subassembly is required, for example, for optical sensors or communication devices, in the case of which a receiver sensitive for electromagnetic radiation and / or a transmitter transmitting electromagnetic radiation are / is accommodated in a housing. For the interaction of the transmitter, or receiver, as the case may be, with the environment outside of the housing, it is necessary to couple electromagnetic radiation into, or out of, the housing. An optical sensor for performing absorption measurements or measurements of attenuated total reflectance, so-called ATR-measurements, can be so embodied, that a radiation source and a spectrometer are accommodated in a h...

AI Technical Summary

Benefits of technology

[0008]Such a mechanical setting of the transparent plug, secured supplementally by casting, assures, compared with the mechanical pressing via a sealing ring, such as described in DE 20 2006 014 464 U1, an increased explosion safety. While a conventional sealing ring would be destroyed in the case of an explosion accompanied by rapid temperature and pressure rise, there can be selected for casting a potting compound permitted in the explosion standards that can withstand these extreme conditions. For achieving sufficient explosion protection, it is furthermore necessary, that there be no crack formation in the transparent plug or development of a gap between the cylindrical lateral surface of the transparent plug and the setting means. Such a crack or gap represents, at the same time, a leak for the pressure-tight housing. If the pressure-tight housing contains, for example, a radiation source and a spectrometer for executing absorption- or ATR-measurements, the transparent plug and the setting means can be subjected to a temperature range between 20 and 60° C. In such a broad temperature range, there is already a significant material expansion. The stresses arising in such case due to the differing coefficients of expansion of the individual components can lead to crack, or gap, formation. Also mechanical shocks can lead to cracks. Compared with the screwing of the transparent plug into the housing wall, such as is described in DE 102 46 762, casting has the advantage that stresses in the radial direction are reduced, or shocks damped, by the cast potting-compound. In this way, the danger of a crack- or gap-formation is lessened compared to the screwed connection into the housing wall known from the state of the art, since such screwed connection is not resilient in the radial direction.

[0025]In a special further development of this embodiment, the optical subassembly forms with the housing wall section, in which the transparent plug is set and with the second housing adjoining the pressure-tight housing, a pressure tight (thus conforming to the explosion protection standards), double-walled covering for the pressure-tight housing. In this case, it is advantageous to provide only one additional housing module. The optical subassembly is then secured by means of the union nut to the other housing module as a double-walled “lid” (compare also FIG. 3), so that a pressure-tightly closed space results.

Problems solved by technology

Such a crack or gap represents, at the same time, a leak for the pressure-tight housing.

The stresses arising in such case due to the differing coefficients of expansion of the individual components can lead to crack, or gap, formation.

Also mechanical shocks can lead to cracks.

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